Hydraulic tappet



Oct. 9, 1945. R. w. JENNY ET AL HYDRAULIC TAPPET Filed Aug. 10, 1942 INVENTOR Roberf WT Jen Hu 0 f. Gil/e Patented Oct. 9, 1945 H RAULIC TAPPET Robert W. Jenny, New Milford, d Hugo E. Glue, Jersey @ity, N. 3., assiora to Wright l nautical Corporation, a corporation of N York Application August 10,1942, Sell No. fitted (oi. tea-cc) 8 Claims.

This invention relates primarily to internal combustion engines and is particularly concerned with improvements in the valve operating mech anism therefor.

It is common practice in valve operating mechanisms to provide a hydraulic pressure means in a to accommodate such changes in the valve clearance. That is, the rior art depended upon inherent leakage of hydraulic fluid from the valve tappet to accommodate a reduction in valve clearance. This is not very satisfactory since obviously the parts of the valve tappet should be made to fit as closely as possible and with aslittle leakage as possible. Accordingly, it is an object of this invention to provide'positive means for changing the quantity of pressure fluid Within the valve tappet to accommodate changes in valve clearance.

Specifically, the invention is applied to a con ventional radial type engine and the movement of the exhaust valve-operating cam is utilized to reciprocate a sleeve surrounding the intake valve tappets to momentarily relieve the hydraulic pressure within these valve tappets. Similarly, the movement of the intake valve-operating cam is utilized to relieve the hydraulic pressure within the exhaust valve tappets after each actuation of these tappets.

A further object of thisinvention is to permit a new adjustment to minimum clearance between each actuation of the valve tappet.

while the other series of com lobes islocated along the cam periphery at it and accordingly would be for the exhaust valves. Valve tappet guides it are mounted on the crankcase it as shown in the drawing. In conventional radial cylinder aircraft engines the intake and exhaust valve tappets for each cylinder are mounted adjacent each other On the engine crankcase. Consequently, after a cam lobe has operated an intake valve tappet for a particular cylinder, an exhaust valve operating cam lobe will pass this intake valve tapjacent series of intakecam lobes located at Further objects of this invention will become apparent in reading the annexed detailed description in connection with the drawing, in which:

Fig. l is a section of the engine crankcase showing the valve tappet in elevation; and

Fig. 2 is a section on the line 22 of Fig. 1. Referring to the drawing, ID is an axial section of the engine crankcase of a radial type aircraft'engine wherein a multi-lobe cam H is provided with two series of cam lobes 12 for the intake and exhaust valves respectively. The one series of cam lobes is located along the cam periphery at It and may be for the intake valves,

pet prior to the next actuation of this tappet. This invention utilizes this movement of the exhaust operating cam lobes to relieve the hydraulic pressure within the intake valve tappet before its next actuation. Similarly, the movement of the intake valve operated cam lobes is utilized to relieve the exhaust valve tappets of hydraulic pressure after each actuation.

- 0nly a single valve tappet assembly constructed according to this invention is illustrated in. the drawing. However, obviously it iscontemplated that each of the intake and exhaust valve tappets for each cylinder be so constructed. Valve tappet it has a cam follower roller 2t mounted at the lower end thereof. A slidable sleeve 22 is provided between the valve tappet It and the guide it. An elongated longitudinal slot 25 in the sleeve 22 and the cooperating screw 26 threaded in the guide it and extending into the slot 25 permits a limited sliding movement or the sleeve 22. A lateral extension 30 on the sleeve 22 for the intake valve is arranged for engagement with the adjacent series of exhaust cam lobes it, as best seen in Fig. 1. Similarly, the sleeve 22 on the exhaust valve tappets, operated by the cam lobes located at the cam periphery it, have an'extension 30 arranged for engagement with the adthe periphery l4.

Tappet member It is provided with a cylinv drical bore It at one end with a piston 32 fitted therein and extending from the open cylinder end. The piston 32 has a spherical seat 3! for engagement with the usual hollow push rod 33.

V A spring 3d extending between the flanged head 35 on the piston 32 and the rear of a counterbore 38 within the bore 19 operates to hold the piston in engagement with the push rod 33. The push rod,.in a conventional manner (not shown), is arranged to open a valve, biased closed, when the valve tappet is actuated by the cam mechanism. A passage 36 extends through the tappet cylinder head to the lower end of the cylindrical bore within the tappet. A check valve 31 is arranged departing from the spirit to permit the flow or hydraulic fluid through this passage into the cylindrical bore is in the tappet and to check the flow oi fluid therefrom.

A source of oil pressure is connected to a passage 29 in the crankcase section It thence to an annular groove 40 in the valve tappet guide ii. A radial passage 42 interconnects this annular groove with an annular chamber between the valve tappet guide It, valve tappet l8, and the upper end of sleeve 22. A longitudinal passageway 44 formed in the sleeve member 22 interconnects this annular chamber 22 and the passage 3a in the valve tappet. The lower end of the passage 44 normally connects with the passage It in the tappet thereby providing an oil tion. A drain passage I4 is provided in the tappet and extends into the cylinder l9 thereof. When the tappet is in the valve closed position, passage N is in alignment with a drain passage It in the valve guide I 3. The sleeve 22 is normally interposed between passages II and 86 to prevent escape of oil from the cylinder l8. However, a passage I! through the sleeve 22 is adapted to be brought in alignment with the passages and 56 when the sleeve 22 is raised by engagement of its extension 20 with a cam lobe. This construction permits the oil to drain out of the cylinder I! when the sleeve 22 is raised. A-spring I9 is provided to restore the sleeve 22 to its lowermost position as determined by the stop 28.

As shown in Fig. 2, the valve tappet is in the valve closed position and oil pressure in the space 80 of the cylinder ll below the piston 22 takes up the clearance in the valve operating mechanism. Passages 42, 44 and 26 provide a flow path for the pressure oil into the space 60 in the cylinder is through the check valve 31'. when a cam lobe located along the cam periphery H operates to raise the valve tappet, check valve 31 prevents the escape of oil from the space 80 'so that this iiuid space 80 operates to take up the clearance in the valve operating mechanism. Aiter the valve tappet has again returned to its valve closed position, a cam lobe on the adjacent series of cam lobes located along the cam periphery 16 engages extension 20 to raise the sleeve 22 and align passages N, 58 and Ill to thereby permit the oil to drain from the space 60. At the same time, raising oi the sleeve 22 operates to disconnec't the oil passage 36 in the valve tappet from the-supply passage 44. As soon as the spring 59 is permitted to restore the sleeve 22 to its lower position, the pressure oil will again enter into the space 80 through the check valve 31 to' take up the then existing clearance in the valve operating mechanism prior to the next actua-- tion of this tappet. The invention thereby provides for a new adjustment in the quantity of oil trapped in the valve tappet after each valve tappet actuation.

While we have described our invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding our invention, that various changes and modifications may be made therein without or scope thereof. We aim in the appended claims to cover all such modifications and changes.

We claim as our invention:

1. In an engine valve operating mechanism, a valve tappet assembly extendible under hydraulic pressure comprising a hollow valve tappet closed at one end and having a slidable piston therein and extending irom the other end thereoi, a, check valve arranged to admit hydraulic pressure fluid into said hollow tappet to extend said piston and to prevent the escape oi said pressure fluid from said tappet, a drain passage for said hollow tappet, a reciprocable sleeve surrounding said tappet and normally positioned to close said drain passage, and means to reciprocate said sleeve relative to said tappet and piston after each actuation of the valve tappet to cause said sleeve to momentarily open said tappet drain passage.

2. In an engine valve operating mechanism, an engine driven valve-operating cam mechanism, a valve tappet assembly extendible under hydraulic pressure comprising a hollow valve tappet closed at one end and having a slidable piston therein and extending irom the other end thereof, a check valve arranged to admit hydraulic pressure fluid into said hollow tappet to extend said piston and to prevent the escape of said pressure fluid 'from said tappet, a drain passage for said hollow tappet, a reciprocable sleeve surrounding said tappet and normally positioned to close said drain passage. and means actuated by said cam mechanism to reciprocate said sleeve after each actuation of thevalve tappet to cause said sleeve to momentarily open said tappet drain passage.

3. In an internal combustion engine with a plurality of cylinders having intake and exhaust valves and engine driven intake and exhaust valve-operating cam means,.the combination of a valve tappet assembly ex endible under hydraulic pressure for each of said intake and exhaust valves, said assembly when extended maintaining a minimum valve clearance, means associated with each valve tappet assembly and operable by the engine cam mechanism after valve tappet actuation to momentarily vent said valve tappet, said means comprising a slidable sleeve surrounding the valve tappet, said sleeve being movable to open a drain passage in the tappet, and a check valve in the hydraulic pressure connection to said valve tappet to prevent the escape of hydraulic pressure fluid from sai valvetappet during tappet actuation.

4. In an engine valve-operating mechanism, a valve tappet assembly comprising a I hollow tappet having a slidable piston therein, means to feed a liquid under pressure into said tappet for extending said piston and maintaining a minimum clearance in said valve-operating mechanism, a, check valve arranged to permit ingress of said liquid into said tappet but preventing egress of liquid therefrom, a drain passage for said tappet, and means comprising a slidable sleeve surrounding said tappet and normally closing said passage, said sleeve being movable relative to said tappet and piston to open said passage between each actuation of said tappet.

5. In an internal combustion engine with a plurality of cylinders having intake and exhaust valves and engine driven intake and exhaust valve-operating cam means, a valve tappet assembly for each ot said intake and exhaust valves, each of said valve tappet assemblies being extendible upon application or liquid pressure aseasr? thereto to maintain a minimum valve clearance, a vent port for each valve tappet assembly, a

movable member associated with each valve taperated by the exhaust valve-operating cam means and the movable members associated with the exhaust valve tappets being operated by the intake valve-operating cam means.

6. In an engine valve-operating mechanism, a valve tappet assembly comprising a hollow tappet and a piston slidably disposed therein, engine operated means for intermittently actuating said tappet assembly, means to feed a liquid under pressure into said tappet to extend said piston to maintain a minimum clearance in said valveoperating mechanism, a drain passage for said hollow tappet, and a member movable relative to said tappet, said member being movable to open said drain passage for a short interval of time only while the tappet is idle between periods 01' tappet actuation.

' I. In an engine valve-operating mechanism, a valve tappet assembly extendible upon application of liquid pressure thereto, engine operated periods of actuation for opening and closing said means for intermittently actuating said tappet assembly, means to prevent the escape of said liquid from said tappet assembly during periods of tappet actuation, a liquiddrain passage for said tappet assembly, and means automatically movable in response to engine operation and while said tappet assembly is idle between drain passage.

8. In an engine valve-operating mechanism, a valve tappet assembly comprising a hollow tappet having a piston slidably disposed therein, engine operated means for intermittently actuating said tappet assembly, means to feed a liquid under pressure into said tappet for extending said piston and maintaining a minimum valve clearance in said valve operating mechanism, a check valve arranged to permit ingress of said liquid into said tappet but preventing egress of liquid therefrom, vent passage for said hollow tappet, and means automatically movable in response to engine operation and while said tappet assembly is idle between periods of actuation for opening and closing said vent passage.

ROBERT W. JENNY.

HUGO E. GILLE. 

